Histomoniasis, also know as blackhead disease, is a protozoan disease affecting farm and other poultry species. The disease causes highest mortality in turkeys affecting frequently the whole flock. In broiler chickens also significant mortality could be observed and be accompanied by high morbidity and decreased zoo-technical performance parameters. Other important poultry species, notably quail, pheasants, guinea fowls are also susceptible to the disease.
Treatment of the Histomoniasis disease through use of chemotherapeutics, most notably nitroheterocyclic compounds, was used in the past, including entheptin, nithiazine, and nitroimidazoles. U.S. Pat. No. 4,000,300 describes the application of aminobenzimidazole derivatives for treatment of histomoniasis; U.S. Pat. No. 4,046,908 describes the use of benzimidasole derivatives; and U.S. Pat. No. 4,025,638 describes use carboalcoxyaminobezimidazole. Also know is the use of arsenic derivatives, like Histostat®, or more specifically nitarzon or 4-nitrophenyl arsenic acid. However, on the ground that these compounds are suspected carcinogens, and their use leads to the accumulation of carcinogenic products in the treated animals, their use was prohibited or limited to a large extend in the USA, Europe, and other important turkey growing regions. Currently, no preventive histomonostat as feed additive or any therapeutic drugs are authorized in the EU to either prevent or to treat histomoniasis in affected flocks. As a result we see a number of reports for new appearances of histomoniasis in turkey and other flocks.
Also known is the use of coccidiostats (for example monensin, salinomycin, diclasuril and etc.) through the whole growth cycle of farm birds species in order to protect from coccidiosis or histomoniasis, but it has been shown that their use has no effect with respect to histomoniasis (6).
Also known are attempts to use of paromomycin as a chemotherapeutic agent for treatment of histomoniasis (3). The disadvantage is the estimated high dose and long treatment needed to achieve limited results. It was demonstrated that when fed continuously at 1000-2000 ppm in feed it reduced the mortality of infected birds, but at these doses side effects due to the use of paromomycin were observed—notably lesions and hypertrophy of the liver. In these trials the infection was achieved by direct oral inoculation of the birds with infected embryonated Heterakis gallinarum eggs and the effect of applying paromomycin on the horizontal spreading of the disease from infected to healthy birds was not evaluated. It has also been attempted to use paromomycin as a chemotherapeutic agent in broiler chickens. Its use in-vivo was rendered ineffective when applied at 200 and 400 ppm in broilers (4).